[Bug 3408] New: Adverse backend may starve other backends from activation

[bugzilla-daemon at icedtea.classpath.org]

http://icedtea.classpath.org/bugzilla/show_bug.cgi?id=3408

            Bug ID: 3408
           Summary: Adverse backend may starve other backends from
                    activation
           Product: Thermostat.next
           Version: unspecified
          Hardware: x86_64
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P5
         Component: Agent
          Assignee: unassigned at icedtea.classpath.org
          Reporter: sgehwolf at redhat.com
                CC: thermostat at icedtea.classpath.org

Created attachment 1633
  --> http://icedtea.classpath.org/bugzilla/attachment.cgi?id=1633&action=edit
Adverse backend.

Thermostat agent allows extensions to be written via Backends. If an adverse
developer registers a bad backend, which never returns from Backend.activate()
every Backend which did not register and activate before the "bad" one will
never get a chance to get properly activated by the Thermostat framework.

See the attached reproducer.

Example run of agent with bad backend:
$ ./distribution/target/image/bin/thermostat agent
INFO - Activator: activating thermostat-process bundles
INFO - Agent$1: Adding backend: Backend [name=Host Memory Backend,
version=1.99.12, vendor=Red Hat, Inc., description=Gathers memory statistics
about a host]
INFO - Agent$1: Adding backend: Backend [name=VM Memory Backend,
version=1.99.12, vendor=Red Hat, Inc., description=Gathers memory statistics
about a JVM]
INFO - Agent$1: Adding backend: Backend [name=Commands (cmd-channel) Backend,
version=Thermostat version 1.99.12, vendor=Red Hat Inc.,
description=Establishes web-socket connections to the microservice endpoint so
as to be able to receive command requests]
INFO - Agent$1: Adding backend: Backend [name=Host Overview Backend,
version=1.99.12, vendor=Red Hat, Inc., description=Gathers general information
about a host]
INFO - Agent$1: Adding backend: Backend [name=VM Basic Monitor Backend,
version=0.1, vendor=Red Hat, Inc., description=Monitor the system for JVM
processes]
INFO - Agent$1: Adding backend: Backend [name=VM GC Backend, version=1.99.12,
vendor=Red Hat, Inc., description=Gathers garbage collection statistics about a
JVM]
INFO - Agent$1: Adding backend: Backend [name=Bad backend, version=0.1,
vendor=Adversary, description=Starves other backends]
INFO - AdverseBackend: I'm going to never return. Bye!
WARNING - VmMemoryVmListener: Unable to determine name of generation 2 for VM
d08c6e3f-cfb8-492a-a67f-f0e8e1dafb16
WARNING - VmMemoryVmListener: Further warnings will be ignored
WARNING - VmMemoryVmListener: Unable to determine name of generation 2 for VM
44781903-3d64-4ab4-bdf5-3f28b67ebd32
WARNING - VmMemoryVmListener: Further warnings will be ignored
WARNING - VmMemoryVmListener: Unable to determine name of generation 2 for VM
9f38e015-4fe9-4424-a2f9-f3b7ebb3b42a
WARNING - VmMemoryVmListener: Further warnings will be ignored

In the above case, host-cpu's backend is never activated. Contrast this with a
run without the attached reproducer:

INFO - Activator: activating thermostat-process bundles
INFO - Agent$1: Adding backend: Backend [name=VM GC Backend, version=1.99.12,
vendor=Red Hat, Inc., description=Gathers garbage collection statistics about a
JVM]
INFO - Agent$1: Adding backend: Backend [name=VM Memory Backend,
version=1.99.12, vendor=Red Hat, Inc., description=Gathers memory statistics
about a JVM]
INFO - Agent$1: Adding backend: Backend [name=Commands (cmd-channel) Backend,
version=Thermostat version 1.99.12, vendor=Red Hat Inc.,
description=Establishes web-socket connections to the microservice endpoint so
as to be able to receive command requests]
INFO - Agent$1: Adding backend: Backend [name=Host Overview Backend,
version=1.99.12, vendor=Red Hat, Inc., description=Gathers general information
about a host]
INFO - Agent$1: Adding backend: Backend [name=Host Memory Backend,
version=1.99.12, vendor=Red Hat, Inc., description=Gathers memory statistics
about a host]
INFO - Agent$1: Adding backend: Backend [name=VM Basic Monitor Backend,
version=0.1, vendor=Red Hat, Inc., description=Monitor the system for JVM
processes]
INFO - Agent$1: Adding backend: Backend [name=Host CPU Backend,
version=1.99.12, vendor=Red Hat, Inc., description=Gathers CPU statistics about
a host]
INFO - Agent$1: Adding backend: Backend [name=System Backend, version=1.99.12,
vendor=Red Hat, Inc., description=Gathers basic information from the system]
INFO - AgentApplication: Agent id: 123f5078-4afb-4047-be3c-08ce3a9670a2
WARNING - VmMemoryVmListener: Unable to determine name of generation 2 for VM
b157788b-d850-433c-bb3e-711894908bbe
WARNING - VmMemoryVmListener: Further warnings will be ignored
WARNING - VmMemoryVmListener: Unable to determine name of generation 2 for VM
9a143a0a-e071-4608-bf15-6963b1c36499
WARNING - VmMemoryVmListener: Further warnings will be ignored
WARNING - VmMemoryVmListener: Unable to determine name of generation 2 for VM
40e2418f-d636-4336-942e-2ce489730845
WARNING - VmMemoryVmListener: Further warnings will be ignored

Note that "Host CPU Backend" never activates in the former case.

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